code: def test_forward_mat_batch(self):
      test_x = torch.randn(3, 4, 3)
      mean = self.create_mean()
      if self.__class__.batch_shape is None:
          self.assertEqual(mean(test_x).shape, torch.Size([3, 4]))
      else:
          self.assertEqual(
              mean(test_x).shape,
              torch.Size([*self.__class__.batch_shape, 4]),
          )
  
file_path: gpytorch/gpytorch/test/base_mean_test_case.py
imports: from abc import abstractmethod
  import torch
  from .base_test_case import BaseTestCase
label_desc: Use image node_id 4 for calling the BaseMeanTestCase obj's underlying member method code with example usage: obj.test_forward_mat_batch() without return types